Cassette Puller

ABSTRACT

A cassette puller for an automated storage and retrieval system that stores biological or chemical samples in freezers maintained at ultra-low temperature (e.g., −80° C.) or cryogenic temperatures includes a vertical sleeve into which the selected cassette is lifted. The cassette puller is mounted to a traveling gantry and transports cassettes from one freezer location to another and to the system input/output module, and also includes an ejection mechanism that inserts and retrieves tube storage racks or plates from a selected shelf on the cassette. Other components such as a rack robot, a tube picking mechanism, a sample identification station, etc. are mounted on the traveling gantry as well.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/381,832, filed on Sep. 10, 2010 entitled “Large Automated Storage and Retrieval System for Storing Biological or Chemical Samples at Ultra-Low or Cryogenic Temperatures”.

FIELD OF THE INVENTION

The invention relates to automated storage and retrieval systems for ultra-low temperature or cryogenic freezer systems used primarily to store biological or chemical samples. In particular, the present invention pertains to a robotic cassette puller that transports cassettes carrying multiple sample tube storage racks or sample storage plates normally stored in a horizontal, ultra-low temperature or cryogenic freezer. The cassette puller also places individual sample tube storage racks or plates on to a selected shelf on the cassette, and retrieves individual tube storage racks or plates from the cassette.

BACKGROUND OF THE INVENTION

Storage of biological and chemical samples is becoming widespread in the biotechnology and medical industries. To preserve many of these samples, the samples must be stored well below normal freezing temperatures. Generally speaking, a regular freezer operates from −5° C. to −20° C., an ultra-low temperature freezer operates from about −50° C. to −130° C. (preferably at about −80° C.) and a cryogenic freezer operates from about −140° C. to −196° C. (the boiling point of liquid nitrogen). The present invention is directed to a large automated storage and retrieval system containing one or more ultra-low temperature or cryogenic freezer bays operating below about −65° C. The freezers are contained within a refrigerated enclosure, preferably maintained at about −20° C.

Most biological samples stored in ultra-low temperature or cryogenic systems are contained in sealed plastic laboratory tubes held in tube storage racks in arrays of, for example, 48, 96 or 384 tubes. In some cases, a two dimensional barcode is adhered to the bottom of the tubes and is able to be read through the bottom of the storage racks. In other cases, a one dimensional barcode is placed on the side of the wall of the tube. It is also typical for the sample storage racks themselves to have a barcode. In all cases, bar coding facilitates data entry into a control system that keeps track of the location of each of the biological samples. In some applications, samples are stored in sample storage plates such as sealed microtitre plates or wellplates, rather than stored in sealed tubes held in a rack.

In the art, it is known to store tube storage racks or plates on vertical shelves in cassettes or in drawers in ultra-low temperature or cryogenic freezer chests that located within a refrigerated (e.g., —20° C.) work space. In these systems, active robotic equipment operates in the −20° C. environment to pull the tube storage racks or plates from the ultra-low temperature or cryogenic freezer for sample retrieval and placement because a −80° C. or colder environment is too cold for reliable operation of active robotic mechanisms. The present invention is directed primarily to an automated cassette puller for use in systems having a bank of horizontal ultra-low temperature or cryogenic freezer chests for storing cassettes having vertically aligned shelves to hold sample tube storage racks or plates. The preferred cassette puller is designed to accommodate storage cassettes as described in co-pending Patent Application No. entitled “Sample Storage Cassette for Ultra-Low or Cryogenic Temperatures” filed on even date herewith, Atty. Docket No. 5436-00019, and incorporated herein by reference.

One object of the present invention is to limit exposure of samples to the warmer −20° C. environment outside of the ultra-low temperature or cryogenic freezer bay when placing samples in or retrieving samples from a storage cassette, ultimately for the purpose of reducing undesirable sample temperature rise. Another object of the invention is to facilitate reliable transportation of sample storage cassettes from one location in one of the freezers to another location in the same or different freezer. Yet another object of the invention is to provide a cassette puller to transport input/output cassettes, such as described in co-pending Patent Application No. , entitled “Input/Output Module and Overall Temperature Control of Samples”, filed on even date herewith, Atty. Docket No. 5436-00017 and incorporated herein by reference. Again, with the intent of limiting exposure of samples to the warmer −20° C. environment outside of the ultra-low temperature or cryogenic freezers bay when placing tube storage racks or plates on a shelf in an input/output cassette, or when removing tube storage racks or plates from a shelf on an input/output cassette, or when transporting an input/output cassette within the −20° C. environment.

SUMMARY OF THE INVENTION

The invention is directed to a cassette puller for an automated storage and retrieval system that stores biological or chemical samples in sample tube storage racks or plates within one or more horizontal ultra-low temperature (e.g., −80° C.) or cryogenic freezers contained within a refrigerated enclosure maintained at a temperature of approximately −15° C. to −30° C. In accordance with one aspect of the invention, the cassette puller is repositionable within the refrigerated enclosure above the one or more freezers, is configured to lift storage cassettes from the one or more freezers, and is further configured to eject selected tube storage racks or plates from a lifted cassette or place a tube storage rack or plate into an empty shelf on a lifted cassette. The cassette puller includes a vertical sleeve into which a selected cassette is lifted from the underlying freezer. One significant purpose of the sleeve is to minimize temperature rise of the samples when the cassette is lifted fully or partially from the freezer. In this regard, the sleeve is desirably capped at its top end to provide a substantially enclosed volume above the freezer into which the cassette is lifted. The sleeve necessarily contains at least one access opening to allow removal of a selected tube storage rack or plate on a shelf in a lifted cassette or to allow placement of a tube storage rack or plate on an empty shelf in the lifted cassette. Motor-operated doors cover the access openings and are opened in order to allow removal of a rack or plate from the cassette or placement of a rack or plate onto an empty shelf on the cassette. It has been found that capping the sleeve significantly reduces convective heat transfer and temperature rise of samples in the lifted cassette when the doors are opened to remove a rack or plate from a shelf in a lifted cassette or place a rack or plate on an empty shelf in the lifted cassette. Without the cap on the sleeve, opening the door creates a strong convective path of warmer (e.g. −20° C.) air through the sleeve. Some or all of the walls of the sleeve may be insulated in order to reduce conductive heat transfer to samples within the sleeve.

In an exemplary embodiment of the invention, the cassette puller includes a cassette lifting block located within the sleeve that includes a clamping latch for latching to the top of a selected cassette. A motor-driven lifting mechanism, such as dual servo motor-driven belt drives, lifts and lowers the lifting block and the cassette to which it is latched. The cassette lifting block preferably contains at least one or two downwardly extending locator pins. The locator pins engage guide holes in a top plate of a selected cassette when the cassette puller sleeve is robotically placed over the cassette in the freezer bay and the cassette lifting block is lowered to latch onto the cassette. Once the cassette is latched, the belt drives lift the cassette into the sleeve. The sleeve in this exemplary embodiment includes an access opening on the front side of the sleeve and another access opening on the rear side of the sleeve to allow an ejector mechanism access to tube storage racks or plates from both the front and rear of the sleeve. To eject or insert a tube storage rack or plate from or onto a shelf in the cassette, the belt drive is controlled to vertically align the selected shelf on the cassette at the height of the ejector mechanism and the access openings in the sleeve. In order to ensure that the cassette is lifted to the precise vertical height, the cassette puller desirably contains a mechanical stop mechanism, such as a pair of motor-driven position reference pins. The position reference pins are located on opposite sides of the cassette puller sleeve and are moved horizontally inwardly to engage position referencing stops on an outside surface of the lifted cassette. The mating relationship between the position reference pins and the geometry of the position referencing stops on the outside surface of the lifted cassette mechanically center the shelf in the proper location for the ejector mechanism and access openings in case control of the belt drives results in slight vertical misalignment. The mechanical stop mechanism can also lock the cassette in the cassette puller when transferring the cassette.

The preferred ejector mechanism includes a front ejector and a rear ejector which are generally horizontally aligned on either side of the sleeve at the height of the access openings. The front and rear ejectors each include lifting fingers for lifting a tube storage rack or plate from a selected shelf in the cassette. Preferably, the front and rear ejectors are driven by motors that are controlled independently. In the exemplary embodiment of the invention, removal of a sample tube rack or plate from a shelf on the cassette is accomplished in accordance with the following steps. The front and rear doors are opened to allow the front and rear ejectors access to the rack or plate on the cassette shelf within the sleeve. Then, the front and rear ejectors are moved inward such that lifting fingers on the front and rear ejectors are located underneath the front and rear sides of the rack or plate and also at or underneath notches in the shelf on the cassette that provide clearance for the lifting fingers. Next, the cassette lifting mechanism lowers the cassette slightly such that the rack or plate sits directly on the lifting fingers of the front and rear ejectors. Then, the front and rear ejectors and the rack or plate are moved forward to present the rack or plate outside of the sleeve. At this point, the rack or plate can be taken by a rack robot that moves individual racks or plates within the refrigerated enclosure or it can be moved to a temporary storage location by a shuttle mechanism.

The cassette will most likely be pulled only partially into the sleeve to eject a tube storage rack or plate from a shelf on a lifted cassette, or place a rack or plate on an empty shelf in a cassette The overall dimensions of the sleeve can be configured so that the ejector mechanism aligns with the lower most sleeve on the cassette when the cassette is lifted completely into the sleeve although this is not a strict requirement of the invention. However, it is desirable to lift the cassette fully into the sleeve in order to transport cassettes from one freezer location to another freezer location or to the input/output module.

In accordance with another aspect of the invention, the cassette puller is mounted on a travelling gantry that provides a range of motion for the cassette puller over each of the horizontal freezer chests in the system as well as the input/output module. Preferably, the cassette puller is able to move in three dimensions with respect to the travelling gantry, thus facilitating efficient operation of the cassette puller once the travelling gantry is parked over an appropriate freezer bay or over the input/output module. In order to reduce sample temperature rise when picking samples from the system, it is desirable that the rack robot travel with the cassette puller and also that a tube picker travel with the cassette puller, which can be accomplished by mounting these components to the travelling gantry as well. The tube picker preferably includes a tube picking chamber maintained at the same ultra-low temperature or cryogenic temperature at which the freezers are maintained. Such a tube picking mechanism is described in detail in co-pending U.S. patent application Ser. No. 13/193,838, filed Jul. 29, 2011, entitled “Tube Picking Mechanisms with an Ultra-Low Temperature or Cryogenic Picking Compartment”, by Julian Warhurst, Bruce Zandi, Alexander Carbone, Frank Hunt, Robert Cloutier, James O'Toole, and Elizabeth Alexander which is incorporated herein by reference. Also, a lid lifter for lifting the lids from the freezer compartments can be mounted to the gantry frame. Preferably, the repositionable gantry moves horizontally along rails in the refrigerated enclosure over the freezer chests and the input/output module. Once the gantry is parked over a selected freezer bay or over the input/output module indexing drives move the cassette puller the parked gantry both in the horizontal Y-axis and X-axis directions and the vertical Z-axis direction. This three dimensional movement of the cassette puller with respect to the parked gantry allows the cassette puller to operate effectively without having to move the entire gantry frame, which as mentioned may contain several heavy components.

Other aspects, features and advantages of the invention will be apparent to those skilled in the art upon reviewing the drawings and following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a refrigerated enclosure maintained for example at −20° C. of the type in which the invention operates.

FIG. 2 is a perspective view of a first embodiment of the invention located within the refrigerated enclosure shown in FIG. 1.

FIG. 3 is a partial sectional view cut from above the freezer chests in FIG. 2 illustrating storage cassettes stored in one of the bays of a freezer chest located within the refrigerated enclosure of FIGS. 1 and 2.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3.

FIG. 5 is a perspective view of a cassette puller constructed in accordance with the first embodiment of the invention mounted to a travelling gantry along with other components such as a rack robot, a tube picking mechanism and a bar code reader.

FIG. 6 is a perspective view of the cassette puller constructed in accordance with the first embodiment of the invention.

FIG. 7 is a perspective view of an exemplary storage cassette for holding tube storage racks or plates.

FIG. 8 is a side view of the cassette puller constructed in accordance with the first embodiment of the invention shown lifting a cassette from a freezer bay.

FIGS. 9 and 10 illustrate the operation of an ejector mechanism on a cassette puller constructed in accordance with the first embodiment of the invention.

FIG. 11 is a side view similar to FIG. 8 illustrating a tube storage rack ejected from a lifted cassette.

FIG. 12 is a top view of the system illustrating that the range of movement of the travelling gantry in the Y-axis direction is sufficient for the cassette puller to hover not only a bank of freezers but also over input/output modules for the system.

FIG. 13 is a perspective view of a cassette puller constructed in accordance with a second embodiment of the invention.

FIGS. 14 and 15 are perspective views of the front side and rear side respectively of the cassette puller constructed in accordance with the second embodiment of the invention.

FIG. 16 is an enlarged, perspective view of a lower portion of the cassette puller constructed in accordance with the second embodiment of the invention.

FIG. 17 is a longitudinal sectional view of the cassette puller constructed in accordance with the second embodiment of the invention.

FIG. 18 is a detailed view illustrating the internal operation of the cassette puller constructed in accordance with the second embodiment of the invention.

FIG. 19 is another detailed view illustrating the engagement of the cassette puller of FIGS. 13 to 18 to the top of a cassette.

FIGS. 20 and 21 illustrate the construction of a cassette lifting block used in connection with the cassette puller constructed in accordance with second embodiment of the invention.

FIG. 22 is a plot of data illustrating the results of temperature rise experiments.

FIG. 23 is a schematic view illustrating the operation of the rack ejector assembly used in the cassette puller constructed in accordance with the second embodiment of the invention.

FIG. 24 is a sectional view illustrating components of the rack ejector assembly used in the cassette puller constructed in accordance with the second embodiment of the invention, and in particular the location of the components prior to operation of the rack ejector assembly.

FIG. 25 is a view taken along line 25-25 in FIG. 24.

FIG. 26 is a view similar to FIG. 24 illustrating inward movement of the front and rear ejectors into the sleeve of the cassette puller.

FIGS. 27A and 27B are sectional views taken along 27-27 in FIG. 26 illustrating the engagement of lifting fingers on the front and rear ejectors with a tube storage rack.

FIG. 28 is a view similar to FIGS. 24 and 26 illustrating the movement of the front and rear ejectors to eject the rack from the sleeve and move the rack onto an ejector plate in front of the sleeve.

FIG. 29 is a view similar to FIG. 28 except that the storage plate has been moved into a shuttling mechanism rather than directly onto the ejector plate.

FIG. 30 is a view similar to FIGS. 28 and 29 illustrating a first tube storage rack located in the shuttling mechanism and a second tube rack in-line with the sleeve access opening.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, FIG. 1 illustrates the outside of a refrigerated enclosure 10 maintained at a temperature of approximately −15° C. to −30° C., preferably about −20° C.; and FIG. 2 illustrates inside the refrigerated enclosure 10. Two sample input/output modules 14 are located in the wall of the refrigerated enclosure 10. Multiple horizontal freezer chests 11 are located within the refrigerated enclosure 10, each including a storage compartment or freezer bay maintained at or below −65° C. under normal operating conditions. Preferably, each freezer chests 11 contains two independently cooled bays. Biological or chemical samples stored in sealed storage tubes held in tube racks or stored in sealed wellplates are stored within the freezer chests 11. In an ultra-low temperature system, the temperature within the freezer chests 11 will be maintained at for example −80° C. In a cryogenic system, the temperature within the chests 11 may be maintained at a temperature as low as −196° C. Refrigeration units 12 (FIG. 1) for the respective freezer chests 11 are located on the exterior of the refrigerated enclosure 10. The phantom lines in FIG. 1 indicate that the size of the refrigerated enclosure 10 as well as the number of freezer chests 11 within the refrigerated enclosure 10 and the requisite refrigeration units 12 can be expanded in order to accommodate the storage needs of the facility.

The refrigerated enclosure 10 provides a low temperature (−15° C. to −30° C., e.g., −20° C.) workspace for an automated storage and retrieval system 16. The automated storage and retrieval system 16 is mounted to a travelling gantry 18 that is driven linearly along horizontal Y-axis rails 20. The gantry 18 moves over and above the top of the freezer chests 11 and also over the input/output modules 14, thus providing the automated storage and retrieval system 16 with access to storage cassettes or input/output cassettes stored in the freezers 11 and input/output cassettes residing in the input/output modules 14. The invention is not limited to the specific configuration of the input/output modules 14. Nevertheless, it is preferred that the input/output cassettes and input/output modules be constructed in accordance with the description in co-pending U.S. patent application Ser. No.______, entitled “Input/Output Module and Overall Temperature Control of Samples”, Atty. Docket No. 5436-00017, filed on even date herewith and incorporated herein by reference.

Referring to FIGS. 3 and 4, an array of storage cassettes 24 are removably located in each freezer chest 11. The cassettes 24 carry samples stored in tube storage racks or plates. It is desirable that the freezer chest 11 contain a nest for separating and guiding the placement of the cassettes 24 into the freezer compartments. Referring now to FIG. 7, the illustrated storage cassette 24 includes several vertical shelves each designed to hold an SBS formatted tube storage rack or plate. FIG. 7 shows the shelves being oriented to accept the racks or plates lengthwise although it may be desirable to orient the shelves to accept the racks or plates widthwise. A retrieval bracket 26 is mounted to the top of the cassette 24. While the storage cassette shown in FIG. 7 is suitable for implementing the invention, it is preferred, as mentioned previously, that the storage cassette and the nesting configuration with the freezer bay be constructed in accordance with the above incorporated, co-pending U.S. patent application Ser. No.______, entitled “Sample Storage Cassette for Ultra-Low or Cryogenic Temperatures”, Atty. Docket No. 5436-00019.

Referring again to FIGS. 3 and 4, each horizontal freezer chest 11 includes at least one lid 22 that must be removed in order to access the cassettes 24 within the respective freezer bay. Normally, the freezer chest 11 will have two lids 22 so that removal of one of the lids 22 will provide access to one bay 13 in the freezer 11 and removal of the other lid will provide access to the other bay in the freezer 11. FIGS. 3 and 4 also show a large conduit or tunnel 28 passing through the wall of the refrigerated enclosure 10. Refrigerant lines between the freezer chest 11 and the refrigeration unit 12 located exterior to the refrigerated enclosure 10 pass through the tunnel 28.

Referring now to FIGS. 5 and 6, the automated storage and retrieval system 16 includes a cassette puller 30 mounted to the gantry 18 which travels along the Y-axis rails 20 to move the cassette puller 30 as well as the other components mounted to the gantry 18 in the Y-axis direction generally for the purpose of parking the cassette puller 30 in the appropriate Y-axis position over a freezer bay to access a storage cassette or input/output cassette or over the input/output module to access an input/output cassette. Note that the specific embodiment shown in FIG. 5 does not include a Y-axis indexing drive for the cassette puller 30 independent from the overall Y-axis drive for the gantry 18. In most applications, however, it will be preferable to include a Y-axis indexing drive for the cassette puller 30 in order to allow Y-axis movement of the cassette puller 30 while leaving the gantry 18 parked stationary over an appropriate freezer bay. The cassette puller 30 is positioned over a selected cassette 24 in one of the freezer chests or over the input-output module 14 by moving the cassette puller 30 in the Y-axis and X-axis direction as necessary. An X-axis drive rail 32 is mounted to the gantry frame 18. The cassette puller 30 includes an X-axis indexing drive 34 for moving the cassette puller in the X-axis direction. As mentioned, the embodiment show in FIGS. 5 and 6 does not include a Y-axis indexing rail and drive. To implement a system with a Y-axis indexing drive, it is suitable to mount the ends of the X-axis indexing drive rail 34 with bearings to a pair of Y-axes rails in the manner similar to the mounting of rail 58 for the rack robot 54 to Y-axes rails 60.

The cassette puller 30 includes a vertical sleeve 38. In FIG. 6, a thermally insulated wall 40 is shown in phantom and generally surrounds the sleeve 38 and a structural frame 42 for the cassette puller 30. The X-axis drive 34 for the cassette puller 30 is mounted to the structural frame 42 for the cassette puller 30, see FIG. 6. A Z-axis slide mechanism 41 is also provided to raise and lower the sleeve about 4 or 5 inches, which facilitates the placement and removal of the sleeve 38 over a location in which a cassette 24 is or will be stored.

Referring now in particular to FIGS. 6 and 8, the cassette puller 30 in this embodiment includes a robotic lifting arm 44 that is driven by a lift motor 46. The lift motor 46 in this embodiment drives a ball screw to move the lifting arm 44 vertically. The lifting arm 44 includes a T-shaped latch mechanism that is positioned through an elongated opening 46 on the retrieval bracket 26 of the cassette 24 (see FIG. 7) and then rotated in order to secure the cassette 24. The cassette 24 is then lifted into the sleeve 38 by raising the lifting arm 44. FIG. 8 shows a cassette 24 containing two storage tube racks 48 after the cassette 24 has been lifted into the cassette puller 30. The sleeve 38 of the cassette puller 30 includes an opening 50 to allow the respective tube rack 48 to be ejected from the cassette 24 in the sleeve 38, or to allow placement of a tube rack 48 into a cassette 24 located in the sleeve 38. A rack ejector 52, FIG. 6, is mounted to the cassette puller 30 for this purpose. The height of the lifting arm 44 is adjusted to the appropriate height depending on which shelf the selected tube rack is located. Ejected racks or plates are set on an ejector plate 53 located outside the sleeve 38 but within the refrigerated enclosure 10.

As shown in FIG. 8, the system also includes a rack robot 54. The purpose of the rack robot 54 is to move tube storage racks or plates 48 from the ejector plate 53 to other components located on the gantry 18. The rack robot 54 also serves to replace tube storage racks or plates 48 from the other components to the ejector plate 53, so that the rack ejector 52 can insert the rack or plate on an empty shelf on a cassette 24 located within the cassette puller 30. The rack robot 54 is driven vertically by a two-stage vertical drive 56, although a single stage drive may be suitable. The two-stage vertical drive 56, as shown in FIG. 5, is driven along rail 58 on the gantry 18 to move the rack robot 54 in the X-axis direction. The rail 58 is driven along rails 60 on the gantry to move the rack robot 54 in the Y-axis direction. FIG. 8 also illustrates a lid lifter 23 mounted on the gantry 18.

Still referring to FIG. 5, the system shown has a first and second tube picking mechanism 62 mounted to the gantry 18. One of the purposes of the rack robot 54 is to shuttle tube storage racks to and from the tube picking mechanisms 62. As mentioned, it is desirable that tube picking occur in a chamber cooled to substantially the same temperature in the freezer chest. A tube identification station 64 is also preferably mounted on the gantry 18. The tube identification system may include a 2D barcode reader, one dimensional barcode reader, and/or means for measuring the height of the tubes. Having the tube picker 62 and the tube ID station 64 mounted on the gantry 18 results in these components being in close vicinity to the cassette puller 30, which reduces exposure of the samples to warmer environment (e.g. −20° C.) in the refrigerated enclosure 10 outside of the freezer chests 11.

In most applications, it is not necessary to actively cool the enclosed volume within the sleeve 38 of the cassette puller 30. However, it may be desirable in some circumstances to actively cool the space within the cassette puller 30. Various types of cooling circuits can be used to provide such cooling. One desirable cooling system comprises what is typically a second stage compressor unit of a two stage ultra-low temperature cooling unit, which would cool the space to approximately −86° C. (CF04K63 model from Copeland). For a cryogenic application, a third stage compressor or liquid nitrogen may be necessary. Alternatively, a second stage compressor unit can be used to pre-cool compressed air from −20° C. to −50° C., and a vortex cooler can be used to cool the air from about −50° C. to −100° C. (Vortek). Other suitable cooling systems may be used as well. The cooling system for the cassette puller 30 may be mounted on the gantry 18 as well.

FIGS. 9 and 10 are sectional views showing a tube rack 48 located within the cassette puller sleeve 38 ready for ejection from the cassette 24 (FIG. 9) and ejected from the cassette puller sleeve 38 (FIG. 10) onto the ejector plate 53 and available for transfer by the rack robot 54. FIGS. 9 and 10 also illustrate that the rack ejector assembly 52 can include a shuttling mechanism 55 to move the rack 48 or plate to another location outside of the cassette puller sleeve 38 thereby allowing the rack robot 54 to retrieve or place racks 48 or plates at two locations on the ejector plate 53. FIG. 11 is a view similar to FIG. 8 showing an ejected tube rack 48 being moved by the rack robot 54.

FIG. 12 is a top view of the system illustrating in particular that the range of movement of the gantry 18 in the Y-axis direction along rails 20 is sufficient for the cassette puller 30 to hover over input/output stations 14. The input/output cassettes may hold for example eight (8), twelve (12) or more tube storage racks or plates. As mentioned, the cassette puller 30 transfers input/output cassettes when loading tube storage racks or plates into the system and when retrieving tube storage racks or plates from the system. Under normal operating conditions, an input/output cassette held in the input/output module 14 and the user hand loads or unloads racks or plates into the cassette while the cassette remains in the input/output module 14. Once loaded, the user closes a door, the input/output module 14 purges and then presents the cassette for processing by the cassette puller 30. Although not shown, it may be desirable to provide a special input/output port that allows one to swap out a fully loaded input/output cassette.

FIGS. 13 through 30 illustrate the construction and operation of a cassette puller 130 constructed in accordance with a second embodiment of the invention. Referring generally to FIG. 13, the cassette puller 130 is parked over an array of cassettes 124 stored within an aluminum nest contained within a bay of freezer 111. The view in FIG. 13 is from the rear side of the cassette puller 130. In addition, the outer housing has been removed in order to better illustrate internal components. The cassette puller 130 is shown in a down position such that the sleeve 138 is aligned and physically engages or nearly physically engages a top edge of the nesting slot in which one of the respective cassettes 124 is stored. A cap 139 is mounted to the top of the sleeve 138 to interfere with convective heat transfer through the sleeve 138. A gantry attachment bracket 112 is attached to a rear sidewall 113 of the cassette puller 130. A Z-axis drive mechanism 141 that moves the cassette puller sleeve 138 vertically is mounted to the gantry attachment bracket 112. The cassette puller 130 and sleeve 138 are lowered by the Z-axis drive 141 in order to begin the process of retrieving a storage cassette 124 from the freezer bay. The Z-axis drive 141 has a stroke of about 4 or 5 inches. The Z-axis drive 141 raises the cassette puller 130 and sleeve 138 to transport cassette puller from one location to another within the refrigerated enclosure 10 such as when the cassette puller 130 moves from one freezer bay to another or from the freezer bay to the input/output module. FIG. 13 also shows an X-axis rail 132 which is part of the travelling gantry. An X-axis indexing drive 133 drives the cassette puller 130 along the rail 132 to move the cassette puller 130 in the X-axis direction.

A cassette lifting block 140 (not shown in FIG. 13 but shown, e.g., in FIGS. 17 through 21) contains a clamping latch that latches to a retrieval catch on a top plate of the storage cassette 124. The cassette lifting block 140 is attached to two pairs of stainless steel belts 141. A pair of servo motors 142 mounted to the cassette puller 130 turns stainless steel rollers which in turn lift and lower the stainless steel belts 141 in order to lift and lower the cassette lifting block 140 and any cassette 124 to which it is latched. Friction between the stainless steel rollers driven by the servo motors 142 and the belts 141 prevents the belts from slipping. Mounting brackets 144 for the servo motors 142 are adjustable in order to allow the tension between the rollers and the belts to be properly adjusted. Although not shown in the drawings, it may be desirable to place insulation along the front or back walls of the cassette puller 130 or around all four walls. The structural walls of the cassette puller wall 130 and sleeve 138 are preferably made of aluminum.

Referring now to FIGS. 14 and 15, FIG. 14 shows the front side of the cassette puller 130 and FIG. 15 shows the back side of the cassette puller 130. Near the bottom of the front sidewall 114 is located a front access opening 116 through which tube storage racks 148 or plates are moved to eject a rack or plate from the cassette 124 or place a rack or plate in the cassette 124. A sliding door 118 covers the opening 16 unless a tube rack 148 or plate is being ejected from the cassette 124 or placed into the cassette 124. A stepper motor 120 with an extending shaft 122 is connected to the sliding door 118, and slides the door 118 open or closed. The stepper motor shaft 122 must be able to lift the sliding door 118 high enough to clear the height of the tallest rack or plate 148 for which the system is designed to store. FIG. 14 shows the rack 148 ejected from the cassette 124 and residing above an ejector plate 162 (see, FIG. 16) on the front side of the cassette puller 130. FIG. 15 shows an access opening 126 for the ejector assembly 152 on the rear side 113 of the cassette puller 130. A sliding door 128 covers the rear access opening 126, and again a stepper motor 130 with an extending shaft 132 attached to the sliding door 128 moves the sliding door 128 up and down. The sliding doors 118 and 128 are normally closed when the ejector assembly 152 is not in use. FIGS. 14 and 15 also illustrate a pair of CCD cameras 134 which are used to collect referencing images of the nesting locations in the freezer chests 111. The ejector assembly 152 includes a front ejector 154 and a rear ejector 156, and the movement of the front ejector 156 and the rear ejector 156 are controlled independently. In FIG. 15, servo motor 158, through a rack and pinion drive, controls the motion of the front ejector 154. Servo motor 160 controls the movement of the rear ejector 156 through a separate rack and pinion drive.

Referring to FIG. 16, the front ejector plate 162 is mounted to the front wall 114 of the cassette puller 130 with cantilevered brackets. The servo motor drive labeled with reference number 164 drives a rack shuttling mechanism 200 which is described below. Servo motors 166 move reference positioning pins 170 (see, FIG. 17) inward and outward.

Referring to FIGS. 17, the steel lifting belts 141 are attached to both sides of the lifting block 140. Insulation 165 is desirably located between the lifting portion of the steel belts 141 to which the lifting block 140 is attached and the return portion of the steel belts 141. Supports 163 shown in FIG. 18 connect to the front and back plates 113, 114.

FIG. 18 shows the cassette 124 being lifted to a height within the sleeve 130 appropriate for ejecting tube storage rack 148E. Reference locating pins 170 on opposing sides of the sleeve 130 are attached to armature 172 which in turn is driven along a linear slide 174 by stepper motor 166. The reference locator pins 170 as illustrated by the arrows on FIG. 18 move inward to engage reference locator dimples 176 in the sidewalls of the cassette 124 and lock the cassette 124 in place. The stepper motors 166 retract the pins 170 prior to lifting or lowering the cassette 124. The stepper motors 166 drive the pins 170 inward to engage the dimples 176 on the cassettes 124 in order to secure the position of the cassette 124 for ejection of a rack 148E or plate, the placement of a rack 148E or plate onto the respective shelf in the cassettes, and for transporting a cassette 124 with the cassette puller 130.

Referring now to FIGS. 19-21, shoulder screws 182 connect the sidewalls 184 of the cassette lifting block 140 to the steel lifting belts 141. The sidewalls 184 are recessed from the path of the steel belts 141 in order to provide ample clearance within the sleeve 138. The shoulder screws 182 are used because they cannot be over tightened and tightening may cause stress fractures in the steel belts 141. A repositionable push block 186 is mounted to a lower housing panel 188 on the lifting block 140. Referring in particular to FIG. 21, a repositionable latch plate 190 is mounted to a bottom facing surface of the lower housing panel 188 via linear bearings 192 that ride on rails 194 attached to the bottom surface on the lower housing panel 188. In FIG. 21, the latch plate 190 is in a latched or locked position. Springs 196 bias the latch plate 190 towards the locked position. The latch plate 190 is connected to the push block 186, and is moved between the locked position and the unlocked position by applying force to move the push block 186. Referring to FIG. 19, servo motors 167 drive pusher arms 198 to move the push block 186. The pusher arms 198 pass through openings 208 in the sidewalls 184 of the cassette lifting block 140 to engage the push block 186. In FIG. 19, the pusher arms 198 have moved to the right and have moved pusher block 186 to the right which is the unlocked position, thereby presenting the enlarged portion of the latch opening 204 in the latch plate 190 over the retrieval catch 206 extending upward from the top plate 190 of the cassette 124. To close the latch plate, servo motor 180 drives the push arms 198 in the direction opposite of the arrows in FIG. 19. The springs 196 bias the bottom plate 190 in the closed or latched position. The pusher arms 198 are cleared in order to enable the cassette lifting block 140 to be lifted along with cassette 124. Note that the reference position pins 170 are also retracted prior to lifting the cassette.

FIG. 22 shows the results of temperature rise testing based on a simulated puller sleeve when a cassette with an open shelf is removed from an ultra-low temperature freezer. In test number 3, the simulated sleeve included no top cover and no bottom cover and a 96 tube storage rack containing 96 water filled tubes was placed in the simulated sleeve. The monitored temperature rise was 8.4° C. over 60 seconds. On the other hand, tests 1, 2 and 4 show monitored temperature rises only about 1.7 to 1.9° C. per 60 seconds if the top or the bottom or both ends of the sleeve are covered. Tests 1 and 2 were then run with a 96 tube storage rack having only five (5) water-filled tubes in the rack such that air was able to flow vertically through the open receptacles in the rack. The sleeve included a top cover in both tests 1 and 2, and included a bottom cover in test 2 but not in test 1. When the sleeve did not include a bottom cover, there was a substantial temperature rise (5.5° C.); however including the bottom cover mitigated the temperature rise significantly (2.8° C.). The poor performance in test 1 is believed to be due to convection air flow within the sleeve, and including the bottom cover reduces the convective air flow and hence improves performance. Finally, the five (5) tube test was re-run but this time putting a hole in the sleeve at a location above the rack to simulate the possibility of a poor mechanical seal at the top of the sleeve. Again, it can be seen that including the bottom cover improves thermal performance (2.6° C. versus 6.5° C.).

FIGS. 23-30 describe the rack ejection procedure. FIG. 23 schematically illustrates the front ejector 154 and the rear ejector 156 preparing to lift the rack 148 (not shown in FIG. 23) from a shelf 214 in a cassette 124 located within the sleeve 130 (shown in phantom) of the cassette puller. In FIG. 23, the front door 118 (shown in phantom) covering the opening 116 (shown in phantom) in the puller sleeve 130 is opened to allow the front ejector 154 access inside the puller sleeve 130. Although not shown, the rear door 128 covering the rear access opening 126 for the rear ejector 156 would also be open to allow the rear ejector 156 access inside the sleeve 130. The front ejector 154 includes lifting fingers 210 that extend forward from the main ejector plate. Likewise, the rear ejector 156 includes lifting fingers 212 that extend forward from its main ejector plate. The shelf 214 on the cassette 124 includes clearance notches 216 for the lifting fingers 210 on the front ejector 154 and clearance notches 218 for the lifting fingers 212 on the rear ejector 156. When the front ejector 154 and rear ejector 156 are moved inward to lift a storage rack, the fingers 210, 212 reside in or below the notches 216, 218 in the shelf 214. The front edge of the shelf 214 includes upwardly extending lips 224 that help to prevent a tube storage rack or plate from sliding off the cassette shelf 214 when the cassette is moved.

Referring to FIGS. 24 and 25, FIG. 24 is a sectional view showing the components of the ejector assembly in a typical position prior to ejection of the rack 148 from the cassette 124. FIG. 25 is a sectional view through FIG. 24 illustrating the location of the front and rear ejectors 154, 156, the front and rear doors 118, 128 and the cassette shelf 214 within the cassette sleeve 138 at this step in the process. Rack and pinion drive 220 is extended so that the rear ejector 156 is outside of the puller sleeve 138 and outside of the door 128 which is shown in a closed position in FIGS. 24 and 25. Rack and pinion drive 222 has positioned the front ejector 154 in a neutral position outside of the sleeve 138 and outside of the door 118 which is also shown in the closed position. The cassette 124 is positioned at an appropriate height for the ejector to access rack 148. Reference position pins 170 are moved inward to engage the reference position dimples 176 on the cassette 124 to hold the rack 148 and shelf on which it sits at the appropriate height for ejection to the ejector plate 162 in front of the cassette puller 130. In FIG. 24, the shuttling mechanism 202 is located in an offset rack (or plate) parking location. The shuttle 202 includes a cart that moves along linear rail 205 between an in-line rack (or plate) parking location directly in front of door 118 and the offset parking location which is the location of the shuttle cart 202 in FIG. 24. A servo motor 200 drives a screw drive 201 to move the shuttle cart 202. Stationary guides for the rack 148 or plate are provided at the offset parking location.

Referring now to FIG. 26 and FIGS. 27A and 27B, with the shuttle 202 lying idle in the offset parking location, the front and rear doors 118 and 128 are raised and the rack and pinion drives 222, 220 move the front and rear ejectors 154 and 156 inward so that the lifting fingers 210 on the front ejector 154 and the lifting fingers 212 on the rear ejector 156 reside below the front and rear edges of the storage rack 148 within the clearance provided by the notches 216, 218, see FIG. 27A. Next, as depicted in FIG. 27B, the cassette puller 130 lowers the cassette 124 so that the rack 148 is lifted from the shelf 214 onto the lifting fingers 210, 212 on the front and rear ejectors 154, 156. Once lifted, the front and rear ejectors 154, 156 move in the direction of dashed arrow 226 to remove the storage rack 148 from the cassette 124 and outside of the cassette puller sleeve 138. Referring to FIG. 28, the rack and pinion drives 222 and 220 have moved the front and rear ejectors 154, 156 to place the tube storage rack 148 at the in-line rack (or plate) parking position over the ejector plate 162 such that the rack robot can transfer the rack or plate to the other components on the gantry such as a tube picking mechanism or a tube identification station. In FIG. 28, the rack shuttle 200 is located in the offset position during the ejection process and is not being used. FIG. 29 shows essentially the same process step as in FIG. 28 except that the shuttle 200 has been positioned in the in-line location prior to the rack 148 being ejected. FIG. 30 shows the shuttle 202 having moved a first ejected plate 148A to the offset location, and another tube storage rack 148B, after it has been ejected, residing on the front and rear ejectors 154, 156 in the inline location. The rack robot can retrieve or place tube storage racks 148 (or plates) at either location. Note that it may be practical for the rack robot to replace a rack such as rack 148A after it has undergone processing from e.g., the tube picker in the offset location, and retrieve a rack such as rack 148B from the in-line location. Then, the shuttle 200 can be moved to the in-line location to place the rack 148A into a cassette 124 on a selected shelf.

In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be inferred therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. The different configurations, systems, and method steps described herein may be used alone or in combination with other configurations, systems and method steps. It is to be expected that various equivalents, alternatives and modifications are possible within the scope of the appended claims. 

What is claimed is:
 1. An automated storage and retrieval system for storing sample tube racks or plates at an ultra-low or cryogenic temperature, the system comprising: a refrigerated enclosure maintained at a low temperature of approximately −15° C. to −30° C., the refrigerated enclosure including at least one sample input/output device for passing samples through a wall of the enclosure; at least one freezer chest located within the refrigerated enclosure, each freezer chest having a freezer bay maintained at or below −65° C. under normal operating conditions when samples are stored in the freezer bay, and each freezer chest having a lid or door that can be opened to allow access into the freezer bay from the top of the respective freezer chest; an array of cassettes removably located in the freezer bay for carrying samples stored in tube storage racks or plates; a cassette puller located in the refrigerated enclosure that places and retrieves cassettes in the freezer bay of the at least one freezer chest, the cassette puller comprising in part a sleeve into which a cassette from the freezer bay in the at least one freezer chest is at least partially lifted, the sleeve containing at least one access opening to allow removal of a selected tube storage rack or plate on a shelf in the lifted cassette or allow placement of a tube storage rack or plate on an empty shelf in the lifted cassette.
 2. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the sleeve contains an access opening on both the front and rear sides of the sleeve, and the cassette puller further comprises an ejector mechanism to remove a selected tube storage rack or plate on a shelf in the lifted cassette or place a tube storage rack or plate on an empty shelf in the lifted cassette.
 3. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 2 further comprising a rack robot that travels with the cassette puller and places storage racks or plates into and retrieves storage racks or plates from the ejector mechanism.
 4. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 3 wherein the cassette puller and the rack robot are mounted on a frame on a gantry that passes over the top of the at least one freezer chest.
 5. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 4 wherein the system further comprises a tube picker that travels with the cassette puller and the rack robot and is mounted on the frame for gantry, and the rack robot transports tube storage racks or plates to and from the tube picker.
 6. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the cassette puller is capable of moving laterally.
 7. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the sleeve is capped at or near the top of the sleeve.
 8. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the sleeve contains at least two insulated sidewalls.
 9. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the sleeve has a height of at least about 3 feet.
 10. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the cassette puller further comprises: a cassette lifting block located within the sleeve that includes a clamping latch for latching to a top of the lifted cassette holding sample tube racks or plates; and a motor-driven lifting mechanism for lifting and lowering the cassette lifting block and the cassette to which it is latched.
 11. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 10 wherein the cassette lifting block contains at least one downwardly extending locator pin for engaging a respective guide hole on a top plate of a cassette when the cassette lifting block is lowered to latch onto the cassette.
 12. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 10 wherein the lifting mechanism comprises at least two servo motor driven belt drives.
 13. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 1 wherein the cassette puller further comprises a mechanical stop mechanism for referencing the height of the cassette within the sleeve.
 14. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 13 wherein a mechanical stop mechanism comprises a pair of motor-driven position referencing pins which are located on the opposite sides of the cassette puller sleeve and are moved inwardly to engage position referencing stops on an outside surface of the lifted cassette and are moved outwardly to disengage from the position referencing stops on the outside surface of the lifted cassette.
 15. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 2 wherein the cassette puller sleeve includes a motor-driven door that covers the access opening on the front side of the sleeve and another motor-driven door that covers the access opening on the rear side of the sleeve, wherein the motors are controlled to open and close the front and back doors.
 16. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 2 wherein the front and rear ejectors are driven by motors that are controlled independently.
 17. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 16 wherein the cassette puller further comprises an access opening on both the front and rear sides of the sleeve, a motor-operated door covering the access opening on the front side of the sleeve, another motor-operated door covering the access opening on the rear side of the sleeve, and a lifting mechanism to lift and lower the cassette; and wherein a sample tube rack or plate on the cassette is removed from a shelf on the cassette in accordance with the following steps: opening the front and rear doors to allow the front and rear ejectors access to the rack or plate on the shelf within the sleeve; moving the front and rear ejectors inward such that lifting fingers on the respective ejectors are located underneath the rack or plate on the shelf at or underneath notches providing clearance for the lifting fingers in the respective shelf of the cassette; using the lifting mechanism to lower the cassette slightly such that the rack or plate sits on the front and rear ejector fingers; and moving the front and rear ejectors and the rack or plate forward to an ejector plate located outside of the sleeve.
 18. An automated storage and retrieval system for storing sample tube racks or plates at an ultra-low or cryogenic temperature, the system comprising: a refrigerated enclosure maintained at a low temperature of approximately −15° C. to −30° C., the refrigerated enclosure including at least one sample input/output device for passing samples through a wall of the enclosure; at least one freezer chest located within the refrigerated enclosure, each freezer chest having a freezer bay maintained at or below −65° C. under normal operating conditions when samples are stored in the freezer bay; an array of storage cassettes removably located in each freezer chest for carrying samples stored in sample tube racks or plates in the respective freezer compartment; a traveling cassette puller located within the refrigerated enclosure for placing and retrieving storage cassettes in the freezer bay of the at least one freezer chest; a tube picker that travels with the cassette puller, the tube picker having a tube picking chamber maintained at a temperature at or below −65° C. under normal operating conditions; and an rack robot that travels with the cassette puller and the tube picker for placing storage racks or plates into and retrieving storage racks from storage cassettes pulled from the respective freezer chests and for shuttling sample tube racks or plates to and from the tube picker.
 19. An automated storage and retrieval system for storing sample tube racks as recited in claim 18 wherein the system includes a plurality of horizontal freezer chests that open from the top of the chest, and further wherein the cassette puller, rack robot and the tube picker are mounted on a repositionable frame that moves along a gantry that passes over the top of the horizontal freezer chests.
 20. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 19 further comprising a lid lifter mounted to the gantry frame.
 21. An automated storage and retrieval system for storing sample tube racks or plates as recited in claim 18 wherein the at least one input/output device comprises at least one bay located within the refrigerated enclosure for holding an input/output cassette that carries tube storage racks or plates being placed into or removed into the refrigerated enclosure, and the travelling cassette puller located in the refrigerated enclosure also places and retrieves input/output cassettes from the input/output bay and transports the input/output cassettes within the refrigerated enclosure as necessary.
 22. An automated storage and retrieval system for storing sample tube racks as recited in claim 20 wherein the gantry frame moves horizontally over the horizontal freezer chests along a linear Y-axis and the cassette puller is able to move along the gantry frame in both the Y-axis direction and directions perpendicular to the Y-axis. 